In 2013, Marcus Martin started all 13 games at center and helped USC rush for 2,419 yards and 29 touchdowns. (AP)

The 49ers signed center Marcus Martin to a four-year deal, the team announced Thursday evening.

Martin (6-3, 321) was the first of three, third-round draft picks (70th overall) by the 49ers in this year’s NFL Draft out of USC.

He played in a total of 38 games (33 starts) over three seasons with the Trojans. In 2013, Martin started all 13 games at center and helped USC rush for 2,419 yards and 29 touchdowns. He was named a team captain, earned consensus First-Team All-Pac-12 honors and was selected the Trojans Offensive Lineman of the Year last season.

“Right now, he’s going to be in the understudy role,” 49ers coach Jim Harbaugh said of Martin last weekend during the team's rookie minicamp. “That’s the expectation that we put on him, to learn and get up to speed as fast as possible, and, put no timetable on it. That’s his expectation right now. Learn the offense.”

“I’m coming in to compete,” Martin said. “I’m learning as much as I can from Kilgore and the rest of the offensive linemen, and I’m trying to soak up as much of the offense as I can and be a great competitor.”